Transmission systems are one example of common hydraulic fluid applications. Fluid pressure (of a liquid or gas) is one element that is monitored to measure performance and to operate such systems.
In an automotive automatic transmission system, for example, electronic controls are commonly used to control the pressure of the hydraulic fluid within the fluid lines. By varying the pressure of the hydraulic fluid in the lines, various elements of the automatic transmission system, including the engagement of individual clutches, may be controlled. For example, by varying the pressure of the hydraulic fluid in the fluid lines, the shift points of the gears may be controlled.